Many different companies produced ARP equipment for sale to the general public as well as businesses. Siebe, Gorman & Co Ltd manufactured nearly everything that could be wanted. The below advert appeared in the booklet "Air Raid Precautions - What to Do In An Emergency" (at the princely sum of 6d). The advert shows the main respirators (gas masks) then available.
News about interesting insignia, ARP related info and period photos that turn up.